You can download almost any streaming video by using just your browser (Firefox or Chrome's) and using their "network inspector" to get the URL of the MP4 file.
FireFox: Open the streaming page > Go to the Menu (the three lines, top right) > Web Developer > Network > Play the video and you should see .MP4 files appear (if not skip forward on the video to load new data) > Right click, copy the URL, paste it in the address bar and then you can save the MP4 directly.
Note: Some may cause a "debug error" that slows the page. Just refresh the page (with the Network debugger open) then try again. Your clicks might be slow to register but be patient.
Chrome: Go to More Tools > Developer Tools > In the middle top of the page click the drop down and select Nexus 7 > Go to the Media tab (on the right hand side) > Click on the video to play > Copy the URL, paste it in the address bar and then you can save the MP4 directly.
I've been using this for years now and it has yet to fail me. It won't work on commercial sites like YouTube/Netflix as they stream small encrypted chunks of data, but all JAV streaming sites are basically playing a raw MP4 when you view them, thus you can download it directly.